Method of manufacturing metal powder



Patented May 11, 1926.

UNITED STATES ennzo snmanzo,

or xYo'ro, JAPAN.

METHOD 0! MANUFACTURTNG METAL POWDER.

Io Drawing.

The present invention relates to a method of manufacturing fine powderof a plastic metal, by putting the plastic metal .such as lead, inpieces in a rotatable vessel, and rotating the vessel so as to causefriction of the metal lumps with each other and with the inner surfaceof the vessel thereby ef fecting the abrasion of the metal pieces. Theobject of this invention is to manufacture spongy chemically re-active,fine lead powder by a simple and cheap process without crushing the sameas has hitherto been the case.

Hitherto, the manufacture of metal powder has been done either bycrushing or grinding the material or by a method, as in the case ofmanufacture of zinc dust, which consists in cooling a mixture of zincvapour with air so that the metal coagulates into a fine powder.

The products of these old processes, however, are coarse-grained andliable to harden on the surface layer. Besides, while the particles ofthe powder obtained by crushing or grinding are generally pressed fiatand are therefore with diificulty acted upon by chemicals, the powderobtained by atomizing and cooling process is only a relatively coarseproduct, which is not chemically reactive. Also the powder which isobtained by filing is not only coarse-grained, but is liable to beimpaired in its purity by the mixture of the particles which wear offfrom the files themselves.

Thus the former products are not best adapted for use in specialchemical purposes, which are aimed at in the present invention.

The present invention consists in rotating a rotatable vessel,containing lumps of metallic lead, in such a manner that the metal lumpsrub against one another, and the inner surface of the vessel, causingabrasion and pulverization of the lumps. The degree of fineness of thepowder can be regulated by regulating the quantity of the metal lumpsput in the vessel.

To give a practical example of manufacturing lead powder according tothe present invention;

A circular hollow cylinder made of iron, inches in diameter and 60inches in length, is horizontally and revolubly mounted. Within thiscylinder is fitted an airblower provided with small holes. Through oneend of the cylinder is provided an orifice Application filed January 30,1922. Serial No. 532,920.

for feeding it with the material, and .at the other end, an orifice todischarge the product.

The cylinder is, at the start, filled with 500 balls of steel, 1 inch indiameter, together with 1,000 kilograms of lead balls of 1.5 inches indiameter. As the abrasion is going on, the cylinder is replenished withlead ball continuously and at a definite speed at a rate of 100kilograms an hour, while air blast having a pressure of 2.5 pounds persquare inch, is sent out of the air-blower. The cylinder is caused torotate at a rate of 15-25 times per minute. account of this rotation ofthe cylinder, the lead balls contained therein get abraded andpulverized .into very fine powder, which is blown out of the cylinderthrough the discharge orifice by means of theair blast from the saidblower, and the lead powder thus blown out is led into a suitablechamber and collected there. By this operation, 100 kilograms per hourof fine powder with an apparent specific gravity of about 2.1 isobtained. The above described arrangement may be modified, and insteadof providing a separate discharge passage, the cylinder body may bepierced through all over with 0 small holes, whence the powdered productmay be blownv out to be collected in any suitable chamber.

The lead powder thus obtained is very fine and has an extensive surfaceso that its apparent specific gravity may be made, in some cases, evensmaller than 1. It easily oxidizes and spontaneously ignites, so that itis necessary to provide with a cooling apparatus to radiate the heatgenerated by friction, when treating easily oxidizable metals, such aslead.

In short, the present invention does not crush, grind 0r file metals,but reduces them into powder by abrasion, pieces of the metal to bepulverized being put in a slowly rotating vessel, and caused to rubagainst one another and the wall of the vessel. The principal advantagesof my invention over the hitherto known processes are as follows 1. Asmall amount of power is required; the process is simpler; and thefineness of the product can be regulated as desired.

2. A very high degree of fineness can be attained, without impairing thepurity of the product.

3. The product being spongy and having extensive surface, has a strongchemical reactivity. It often oxidizes in the air and spontaneouslyignites. It is therefore most suitable for chemical purposes and iseconomical too.

4. The product oxidizes at a low temperature, but its catalytic actionis very strong due to its extensive surface and consequently is veryuseful as a catalyzer,a depolarizer of electric battery, a reducingagent, or

as an oxygen carrier.

and forming said lead owder by attrition of said lead masses resu ting,from the rubbing of said masses against each other.

2. A method of forming a finely divided chemically reactive lead powderof such fineness and activity as to be readily changed chemically on exosure to air, which comprises introduclng relatively large masses oflead into a rotatable vessel, rotating said vessel at a relatively lowspeed, introducing a current of air into said vessel, forming said leadpowder. by attrition of said lead masses resulting 'from the rubbing ofsaid lead' masses against each other, and removing the said powder fromsaid vessel by means of said current of air.

In testimony whereof I have aflixed my signature.

GENZO SHIMADZU.

